Solar concentrator construction

ABSTRACT

The solar concentrator includes a base with a support frame that is rotatably connected thereto. A torsion box is tiltably mounted to the support frame to provide a wide range of movement of the torsion box and the finish surface thereon, which is preferably of a single plane parabolic shape that carries linear mirror strips. A receiver is mounted above the surface of the mirror strips at the focus of the parabola by a bracket to optimize reflection of radiation thereto. Plumbing transports liquid, such as water, through the receiver for heating thereof for various purposes, such as water desalinization. Thus, the solar concentrator is an optimized low cost and easy to manufacture solar concentrator.

CROSS REFERENCE TO RELATED APPLICATION

This application is related to and claims priority from earlier filed provisional patent application Ser. No. 61/483,141, filed May 6, 2011, the entire contents thereof is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to power generation systems. In particular, the invention relates to a solar thermal power plant using solar heat energy in a direct steam generation (DSG) process, wherein a liquid phase of a phase changing fluid (e.g. water) is provided by a pressure vessel to a boiler tube where concentrated solar radiation heating takes place, and a gaseous phase of a phase changing fluid (e.g. steam) is cycled back to the pressure vessel, so as to enable flow control under rapidly varying solar heating transients and two-phase working fluid instability conditions, and to enable heat energy storage in the pressure vessel for later use in the production of electrical or mechanical power as well as space/water heating.

Solar thermal power plants and systems using DSG processes are known for use in various applications, including for example powering a steam turbine and generating electricity. DSG processes have particular application in the purification of water, desalinization and generation of electricity, for example. DSG systems typically use solar concentrators or collectors, such as parabolic trough collectors or dish collectors known in the art, to focus solar radiation onto a vessel or tube in which, for example, water is flowed or otherwise present, to heat the water into steam. In such systems, work is then typically produced by expanding the steam in an expander, such as a turbine, after which the working fluid may be condensed in a condenser for recirculation in the case of closed systems, or expelled in the case of open systems.

It is well known in the industry that a large portion of the cost and effort in manufacture is directed to the construction of the solar concentrator body itself. This is because it is critical for the solar concentrator to be as stable and vibration-proof as possible so that it may provide a solid substrate base for receiving and supporting the important mirrored surface thereon. It is well known in the art to provide a solar concentrator in the form of a steel exoskeleton that carries cement thereon in the form of the desired parabolic shape. The surface of the cement face of the concentrator is coated with the desire mirrored glass material to provide the needed reflectivity to direct radiation to the fluid filled tubing or chamber for heating. As can be understood, this custom mirrored glass is very expensive and the large cement base is extremely heavy. As a result, these prior art solar concentrators that are known in the art are very expensive and cumbersome.

In summary, there is therefore a need for a DSG type solar thermal power generation system with a solar concentrator that is less expensive and cumbersome than prior art solar concentrator yet still provides superior radiation directing performance. There is a need for a solid structure that is rigid and can hold its shape yet still provides the needed mirrored surfaces for reflection of radiation, as required. There is a further need for a solar concentrator that has a long shelf life with relatively low tolerance. There is a need for a solar concentrator that is easier and quicker to manufacture and assemble compared to prior art concentrators. Moreover, there is a need for a solar concentrator that is durable and non-corrosive. There is a need to replace expensive mirrors with low iron float mirrors. Finally, there is a need to replace prior art steel exoskeletons with fiberglass composite materials.

SUMMARY OF THE INVENTION

The present invention preserves the advantages of prior art solar concentrators for the purposes of making direct steam. In addition, it provides new advantages not found in currently available solar concentrators and overcomes many disadvantages of such currently available solar concentrators.

The present invention provides a solar concentrator that includes a base with a support frame that is rotatably connected thereto. A torsion box is tiltably mounted to the support frame to provide a wide range of movement of the torsion box and the finish surface thereon, which is preferably of a single plane parabolic shape that carries linear mirror strips. A receiver is mounted above the surface of the mirror strips at the focus of the parabola by a bracket to optimize reflection of radiation thereto. Plumbing transports fluid through the receiver for heating thereof to provide an optimized low cost and easy to manufacture solar concentrator.

It is an object of the present invention to provide a novel and unique solar concentrator that is less expensive to manufacture than prior solar concentrators.

There is a further object of the present invention to provide a solar concentrator that is lighter in weight and easier to manufacture and assemble.

Another object of the present is to provide a solar concentrator that can be positioned as needed, such as in two axes of rotation, for optimal tracking of the sun.

A further object of the present invention is to provide a solar concentrator that employs standard commodity parts and components to help reduce cost of construction of the solar concentrator.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features which are characteristic of the present invention are set forth in the appended claims. However, the invention's preferred embodiments, together with further objects and attendant advantages, will be best understood by reference to the following detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a front perspective view of the solar concentrator of the present invention;

FIG. 2 is a front view of the solar concentrator of the present invention;

FIG. 3 is a front perspective view of the solar concentrator of the present invention prior to installation of the glass mirror strips;

FIG. 4 is a front view of the solar concentrator of the present invention prior to installation of the glass mirror strips;

FIG. 5 is a close-up front perspective view with one glass strip installed on the top surface of the solar concentrator;

FIG. 6 is a side view of the solar concentrator of the present invention with receiver installed;

FIG. 7 is a top view of the solar concentrator of the present invention showing the array of mirror strips; and

FIG. 8 is a representational view of the two different directions of movement of the solar concentrator of the present invention.

FIG. 9 is a side view of the solar concentrator of the present invention in a first tilted gimbal position;

FIG. 10 is a side view of the solar concentrator of the present invention in a second tilted gimbal position;

FIG. 11 is a side view of the solar concentrator of the present invention in a third tilted gimbal position;

FIG. 12 is a rear view of the solar concentrator of the present invention showing the piston for controlling gimbal tilt; and

FIG. 13 is a front perspective view of the base with support for the support frame.

DETAILED DESCRIPTION OF THE INVENTION

Turning first to FIGS. 1 and 2, a front perspective and front view of the solar concentrator 10 of the present invention is shown. The solar concentrator 10 includes a base 12 with a support frame 14 rotatably connected thereto to permit rotation of the solar concentrator 10 about an axis that is substantially perpendicular to the ground 16. The support frame 14 includes two arms 18 with only one shown in the figures with the opposing arm being a mirror image thereof. A torsion box 20 is pivotally mounted to the support frame 14 via the arms 18, namely via pins 22 emanating from opposing sides of the torsion box 20 that pivotally engage with respective apertures 24 through the free ends of the arms 18. While this configuration is preferred to enable pivoting, it may be reversed with pins on the support arms 18 and apertures on the torsion box 20 or another structure and still be within the scope of the present invention.

As will be described in detail below, the torsion box 20 is parabolic through one plane is made of hollow fiberglass and carries an array of glass mirror strips 26 thereon. A receiver 28 is mounted at the focal point of the parabolic-shaped torsion box 20 to focus reflected light for heating of fluid passing through the receiver. Water is preferably used for the fluid. Receiver support/bracket 30 is employed to position the receiver 28 where desired and plumbing 32 is used to transport fluid passing through the receiver 28. The receiver support 30 may be, for example, a 40 inch steel or carbon fiber I-beam. The receiver 28 may be blackened copper pipe with a Pyrex jacket and a liner trip of a triple junction photovoltaic cell. Such a configuration enables the receiver 28 to be elevated above the surface 21 of the solar concentrator 10 at the precise location of the parabolic focal point (i.e. liner focus) to optimize reflection of radiation from the surface of the solar concentrator 10.

Turning now to FIG. 3, a front perspective view of the solar concentrator 10 of the present invention is shown prior to installation of the glass mirror strips 26. FIG. 4 shows a front view thereof. A torsion box 20, preferably fiberglass, is provided as a substrate to support the fiberglass finish 21 thereon. The torsion box 20 provides a rigid structure so that the overall shape of the solar concentrator 10 is maintained. The torsion box 20 can be filled with sand or other material (not shown) to add weight thereto to help reduce undesirable vibration due to wind, and the like. Preferably, the solar concentrator 10 has a parabolic shape in one direction, i.e. a curved shape in one plane rather than a circular paraboloid shape where the surface is defined by a parabola traveling along its axis one in more than one plane. The single direction/plane parabolic configuration is preferred over a circular paraboloid to save costs, as it is easier to construct such a parabolic shape compared to one that is in more than one plane. This is because a circular paraboloid include no straight lines at all. In contrast, a single direction/plane parabolic configuration includes straight lines running in one direction. In the parabola used in the present invention, the straight lines run vertically, namely perpendicular to the ground 16. However, it should be understood that the orientation of the parabola could be changed as desired by orienting the torsion box 20 in a different direction.

FIG. 5 is a close-up view of the top fiberglass finished surface 21 that is carried by torsion box 20. In FIG. 5, mirror strips 26, preferably low iron-float glass, are adhered to the top fiberglass finished surface 21 by an adhesive, such as an epoxy. As can be seen in FIGS. 1, 2 and 7, these glass mirror strips 26 are preferably arranged in parallel and closely adjacent to one another across the width of the top surface 21 of the solar concentrator 10. These mirrored glass strips 26 are standard mirror strips that are inexpensive and easy to install. Placing the strips 26 vertically across the width of the parabolic surface enables flat mirror strips 26 to be used thereby avoid custom mirror members that are curved or coating an entire surface that is curved with mirrored material. Thus, straight and flat mirror strips 26 are used in the present invention to simulate or approximate a curved parabolic mirror surface of that found in the prior art.

Since an array of strips 26 are employed in the present invention, any given mirror strip 26 can be independently replaced for a localized repair obviating the need for a costly resurfacing of the mirror, which would be required in prior art solar concentrators that include a custom mirror surface. FIG. 7 also illustrates that the overall dimensions of the solar concentrator 10, namely the finished surface 21, are preferably 10 feet in width and 8 feet in height. While these dimensions are preferred, the finished surface that can carry mirror strips 26 of the solar concentrator 10 of the present invention can be constructed of any size or shape.

The torsion box 20 can best be seen in FIGS. 5, 9-11, where the rigid fiberglass structure provides a solid support for the fiberglass finish surface 21 as well as the support of the strips 26 of mirrored glass adhered thereon. The solar concentrator can both tilt relative to the ground and also rotate about an axis perpendicular to the ground. The two different directions of movement of the solar concentrator, namely two-axis tracking, can be seen by the representational figure of FIG. 8.

Referring first to the tilting ability, the torsion box 20 includes gimbal mounting pins 22, which are received by arms 18 of a support frame 14 that is, in turn, rotatably mounted to a base 12, as seen in FIGS. 5, 9-11, which rotates about an axis that is perpendicular to the ground. More specifically, the two gimbal mounting pins 22 are respectively rotatably received in two mounting holes 24 in the base, as seen in FIG. 1. It is also possible to add sand bags to the base to help reduce vibration from wind, and the like. This enables the solar concentrator 10 to tilt about an axis that is parallel to the ground. FIG. 9 shows the torsion box 20, with mirror strips 26 thereon, in a very upright almost vertical position. FIG. 10 shows the torsion box 20 tilted into an angled position while FIG. 11 shows a substantially horizontal position of the torsion box 20 to enable the mirror strips 26 on the finish surface 21 to point directly upward to the sky. FIGS. 9-11 illustrate the flexibility and range and tilting motion of the solar concentrator 10.

As described above, the torsion box 20 tilts relative the support frame 14. For precision and automated control of such tilting action, an actuator or worm drive 34 is attached to the solar concentrator 10 to controllably tilt the solar concentrator about the gimbal mounting pins. For example, one end 34 a of the actuator 34 is secured to the torsion box 20 and the opposing end 34 b is secured to the support frame 14.

Similarly, for precision and automated control of the rotational action of the support frame 14 relative to the base 12, as seen in FIG. 13, a motor 36 is attached to the base to enable horizontal rotation about an axis that is perpendicular to the ground. A light sensor or “sunseeker” may be employed to automate the tracking of the sun so that the solar concentrator 10 is always pointed in the optimal direction. For example, 180 degree rotation of the solar concentrator 10 can be achieved. The support frame 14 sits on top of ball bearings 38 so that it may freely rotated relative to the base 12. The motor 36 is representationally shown to indicate that the movement of the support frame 14 relative to the base 12 is preferably motor assisted.

The foregoing mechanisms for controlling tilting and rotational movement of the solar concentrator 10 are so well known in the art that they need not be discussed in further detail herein.

In view of the foregoing, a new and novel improved solar concentrator is provided by the present invention that addresses the shortcomings of prior art solar concentrators.

It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims. 

1. An improved solar concentrator, comprising: a hollow torsion box having a top surface, height and width with a single plane parabolic shape across the width thereof; the single plane parabolic shape having a focal point; a plurality of substantially flat mirror strips affixed to the top surface of the hollow torsion box and positioned vertically across the length thereof in parallel with each other; and a receiver affixed to the hollow torsion box and located approximately at the focal point.
 2. The improved solar concentrator of claim 1, wherein the hollow torsion box is made of fiberglass.
 3. The improved solar concentrator of claim 1, where the hollow torsion box is filled with particulate material.
 4. The improved solar concentrator of claim 3, wherein the particulate material is sand.
 5. The improved solar concentrator of claim 1, wherein the plurality of mirror strips are affixed by an adhesive to the top surface of the torsion box.
 6. The improved solar concentrator of claim 1, wherein the receiver includes a pipe configured for the transport of liquid.
 7. The improved solar concentrator of claim 1, further comprising: a pair gimbal mount pins respectively affixed to opposing sides of the torsion box; a support frame defining a pin holes respectively located on opposing sides of the frame configured for respective receipt of the pair of gimbal mount pins to provide a gimbal mount; a base; the support frame being rotatably mounted to the base.
 8. The improved solar concentrator of claim 7, further comprising: means connected to the support frame and torsion box for mechanically controlling the gimbal mount.
 9. The improved solar concentrator of claim 8, wherein the means connected to the support frame is selected from the group consisting of an actuator and a worm drive.
 10. The improved solar concentrator of claim 7, further comprising: means connected to the base for mechanically rotating the support frame and torsion box gimbal-mounted thereon relative to the base.
 11. The improved solar concentrator of claim 10, wherein the means connected to the base is a motor. 